Optical device for measuring the roll angle of a projectile

Abstract

This optical device comprises, at the rear of the projectile (3), a catadioptric system (15) equipped with a polariser (16) and, at the firing station of the projectile (3), a light source (5) whose beam illuminates the rear of the projectile (3) and a light-flux analyzer (6) calculating from the polarization direction of the light flux reflected by the projectile (3) the roll angle of the latter. It is noteworthy in that it comprises, in order to remove the ambiguity of π from the measurement of the roll angle, a reflector dihedron (20) which is positioned along the side of the projectile and which reflects the light beam from the source (5) back to the light-flux analyzer (6) once per turn of the roll of the projectile (3) when the light source (5) is not blocked from it by the body of the projectile (3).

We claim: 
     
       1. An optical system for measuring the roll angle of a projectile, comprising: means for launching the projectile;   a light source located at the launching means for projecting a light beam toward a launched projectile, along an axis laterally offset from an axis of the beam, and illuminating the rear of the projectile;   catadioptric means mounted to the rear of the projectile for reflecting light back from the source;   a polarizer located at the rear of the projectile, intermediate the catadioptric means and the launching means, for polarizing light reflected back toward the launching means;   a dihedron reflector positioned on a radially outward section of the projectile, and having an edge normal to the roll angle of the projectile, for producing a pulse of light reflected back to the source, once for each complete roll of the projectile, when the source and dihedron reflector are unobstructed by the projectile body;   and light flux analyzer means located at the launching means for calculating projectile roll angle from the polarization direction of the light flux reflected back from both the catadioptric means and the dihedron reflector, at the rear of the projectile.   
     
     
       2. The system set forth in claim 1 wherein the flux analyzer means comprises: first optical means for measuring the light flux directly reflected from the rear of the projectile;   second optical means for measuring the polarized light flux reflected from the rear of the projectile, via the polarizer;   first circuit means compensating for the fluctuations of light flux due to turbulence, and splitting a signal supplied by the second optical means; and   second circuit means, utilizing a signal from the first circuit means for calculating the roll angle.